Butterfly valve

Abstract: A butterfly valve with a disc (1) having two separate side-by-side peripheral edges (3,4) separated by a channel (5). The peripheral edges (3,4) are eccentrically disposed to one another and seat with a suitably shaped valve seat (2) e.g. a sealing ring having one or more outlets (24,25). If one of the edges (3 or 4) leaks e.g. due to damage or a trapped particle, the fluid is prevented from passing to the other side of the disc by the second edge (3 or 4) and drains away along the channel (5) through the or each outlet (24 or 25). Thus the danger of unwanted mixing or contamination is reduced.

Description: This invention relates to a butterfly valve. Conventionally a butterfly valve comprises a disc and a seat such as an annular elastomeric seal against which the disc engages when the valve is closed. Sometimes, either the disc edge or the seat is damaged, or particulate matter becomes wedged between the disc edge and the seat, and leakage of fluid occurs. In some situations a small amount of leakage can be tolerated but in others it is definitely not, particularly when contact or mixing of materials which would otherwise be separated by the valve disc can have dangerous consequences. In order to overcome this problem it has been proposed to use a valve having two discs spaced apart longitudinally along the channel through which fluid is flowing, the two discs being linked together mechanically so as always to be parallel with one another. This arrangement is intended to ensure that if leakage of fluid past one disc occurs, then the other prevents further leakage or flow. However the provision of two discs and a linkage which accurately maintains the parallel arrangement for two discs at all angles from the open to the closed position is expensive and since the linkage is positioned outside the valve body is likely to become damaged, thus causing one disc to no longer be parallel to the other. DE-C-1096134 discloses a flap valve positioned in a valve body, the flap comprising two parallel elastically deformable lips for sealingly engaging the interior of the valve body in the closed position and a channel located between the lips which connects to an outlet in the valve body in the closed position whereby any fluid leaking past one lip flows along the channel and out through the outlet. GB-A-1512482 discloses a butterfly valve according to the precharacterising part of claim 1. Since the two peripheral edges are centred on the same axis, on closing, one edge has to be pushed past the deformable seating surface for the other edge. This causes excessive wear and possible damage to the edge(s) and/or seating surface(s). Furthermore, unless a mechanical stop is provided, it is easy to rotate both edges beyond their respective seating surfaces. It is an object of the present invention to provide a butterfly valve construction which overcomes or reduces the effects of the above problems. In accordance with the invention a butterfly valve comprises a body, a valve disc disposed in said body for sealing engagement with a valve seat of deformable material associated with said body, wherein the valve disc has two parallel peripheral edges, each of circular form in the open and closed conditions of the valve, a channel being defined between said peripheral edges which connects to an outlet, whereby when in a closed position any fluid leaking past one peripheral edge of the disc flows along the said channel and to the outlet characterised in that the centres of the two parallel peripheral edges are eccentrically disposed with respect to the rotational axis of the disc in the open and closed conditions of the valve, the centre of one edge being disposed on one side of the rotational axis of the disc and spaced apart therefrom by a preset distance measured in the plane of the disc and the centre of the other edge being disposed on the other side of the rotational axis of the disc and spaced apart therefrom by a distance measured in the plane of the disc equal to said preset distance, the valve seat having two generally cylindrical seating surfaces eccentrically disposed with respect to one another against which each of the two peripheral edges respectively seats in the closed condition of the valve. Preferably the outlet e.g. a drain or vent comprises at least one port formed in the valve seat. Preferably also the outlet is positioned to communicate with the channel in the closed position of the valve. Further the seat may be in the form of a sealing ring and the outlet leads through the sealing ring to the exterior of the valve. Preferably the two circular forms of each of the peripheral edges, which may be of equal diameter, are interrupted by flat surfaces adjacent to the two diametrically opposed positions where the disc is connected to one or two shafts. The flat surfaces may also interrupt the channel between the two edges and if this is so at least one groove may be provided in the flat surface to connect the interactive parts of the channel. Preferably the valve seat comprises an annular elastomeric sealing ring formed with the two generally cylindrical surfaces, each engageable by a respective edge of the disc in the closed position. One embodiment of the invention will now be described by way of example only with reference to the accompanying drawings of which:- Figure 1 shows a schematic plan view of the valve disc in contact with the valve seat (which is shown in cross-section); and Figure 2 shows a side view of the valve disc. As shown in the drawings, the valve comprises a valve disc 1 and a valve seat 2. The disc 1 is formed with two peripheral edges 3, 4 each having a rounded profile for sealing engagement with the valve seat 2. Between the two edges is formed a peripheral channel 5. The disc is formed with two diametrically opposed bosses 6 and 7, having blind bores 8 and 9 extending inwards from the disc periphery. One bore 8 is adapted to receive a drive shaft (not shown) to which a torque may be applied to rotate the disc about the axis 0-0 between the opened and closed positions. Means, not shown, is provided to prevent the drive shaft rotating in the bore and thus effectively transmit torque from the shaft to the disc. The other bore 9 receives a stub axle (not shown) on which the disc is free to rotate. The bosses interrupt the edges 3, 4 and the channel 5. As can be seen in Figure 2, the edges merge with the outer flat faces 10, 11 of the bosses 6, 7. The channel 5 merges with two short shallow grooves 12, 13 extending to the edges of the flat surface of the boss 6 for receiving the drive shaft, the two grooves being diametrically opposed with respect to the rotational axis O-O and extending generally in the central plane P-P of the disc. The two grooves 12 and 13 join a shallow circular groove 14 which is positioned to lie coaxially with the axis O-O and to surround the blind bore 8. The flat surface 11 of the boss 7 for receiving the stub axle is similarly formed with two short grooves 15, 16 and a circular groove 17, the grooves 15, 16 and 17 all communicating with the channel 5. The base of the channel 5 is circular in cross-section as can be seen in Figure 2, being centred at point B which lies on the rotational axis O-O of the disc and mid-way between the two flat surfaces 10, 11. The diameter 19 of the base 18 of the channel 5 is shown by a solid line in Figure 2. The edges 3 and 4 are each of circular form as can be seen in Figure 2 except where they are interrupted by the flat surfaces 10 and 11. One edge 3 has its centre at point C midway between the two flat surfaces 10 and 11 and offset by a small preset distance B-C from the rotational axis O-O. The small preset distance B-C is measured in the plane of the disc. The diameter 21 of the edge 3 is shown by a dotted line. The other edge 4 has its centre at point A midway between the two flat surfaces 10 and 11 and is offset a small preset distance A-B from the rotational axis O-O but on the opposite side to the point C. Again, the small preset distance A-B is within the plane of the disc. The diameter 20 of edge 4 is shown by a chain dotted line. The preset distance between points A and B measured in the plane of the disc equals the preset distance between points B and C. Thus the two edges 3 and 4 are eccentrically opposed to one another and to the axis O-O. The valve seat 2, shown in Figure 1, comprises a ring of elastomeric material bonded to a suitable support surface (not shown) formed on the interior of the valve body. The valve seat has two inner surfaces 22, 23 each of cylindrical form except where the seat engages the flat surfaces 10 and 11 of the disc and eccentrically disposed with respect to one another so as to sealingly engage with the two edges 3 and 4 respectively. The surface 22 is concentric with edge 3 and the surface 23 is concentric with edge 4. The inner diameters of the surfaces 22 and 23 are each slightly smaller than the outer diameters 20, 21 of the edges 3, 4 so that when the disc 2 is in the closed position as shown in Figure 1 the elastomeric material is compressed and a good seal obtained between each edge 3, 4 and respective contacting surfaces 22, 23. As shown in Figure 1, at the junction between the surfaces 22, 23 and the central plane P-P of the seat and the disc (in the closed position) one or more ports 24, 25 are provided through the thickness of the seat 2. The or each port also passes through the valve body to the valve exterior or to a reservoir within the valve body. The or each port is closed by suitable means (not shown) when the valve is in the open position. As will be realised the valve disc 1 can only be moved from the closed position as shown in Figure 1 towards the open position by rotational movement in one direction i.e. clockwise as indicated by the arrows X and Y. Furthermore, on closing the valve, (i.e. with an anti-clockwise rotation) it is not possible to move the edges 3 and 4 beyond the respective seating surfaces 22 and 23 because of their eccentric disposition. In use when the valve is in the closed position shown in Figure 1, if fluid leaks past one edge e.g. 3 it will pass into the channel 5 and then drain away through the or each port 24, 25 to the valve exterior or a reservoir, if necessary along the shallow grooves 12, 13 and 14 and/or 15, 16 and 17 formed in the surfaces 10, 11 of the bosses 6, 7 respectively. The fluid will be prevented from flowing to the other side of the disc by the sealing effect of the other edge e.g. 4. Because the two edges are integrally formed with the disc they are always accurately parallel to one another i.e. parallel to the central plane P-P of the disc.

Claims: A butterfly valve comprising a body, a valve disc (1) disposed in said body for sealing engagement with a valve seat (2) of deformable material associated with said body, wherein the valve disc has two parallel peripheral edges (3,4), each of circular form in the open and closed condition of the valve, a channel (5) being defined between said peripheral edges (3,4) which connects to an outlet (24 or 25), whereby when in a closed position any fluid leaking past one peripheral edge (3 or 4) of the disc flows along the said channel (5) and to the outlet (24 or 25), characterised in that the centres (C,A) of the two parallel peripheral edges (3, 4) are eccentrically disposed with respect to the rotational axis (O-O) of the disc (1) in the open and closed conditions of the valve, the centre (C) of one edge (3) being disposed on one side of the rotational axis (O-O) of the disc (1) and spaced apart therefrom by a preset distance (B-C) measured in the plane of the disc and the centre (A) of the other edge (4) being disposed on the other side of the rotational axis (O-O) of the disc (1) and spaced apart therefrom by a distance (A-B) measured in the plane of the disc equal to said preset distance (B-C), the valve seat (2) having two generally cylindrical seating surfaces (22, 23) eccentrically disposed with respect to one another against which each of the two peripheral edges (3,4) respectively seats in the closed condition of the valve. A butterfly valve according to claim 1 characterised in that the outlet (24 or 25) comprises at least one port formed in the valve seat (2). A butterfly valve according to either of claims 1 or 2 characterised in that the outlet (24 or 25) is positioned to communicate with the channel (5) in the closed position of the valve. A butterfly valve according to any one of claims 1, 2 or 3 characterised in that the seat (2) is in the form of a sealing ring and the outlet (24 or 25) leads through said sealing ring to the exterior of the valve. A butterfly valve according to any one of the preceding claims characterised in that the two circular forms of each of the peripheral edges (3,4) are of equal diameter. A butterfly valve according to any one of the preceding claims characterised in that the two circular forms of each of the peripheral edges (3,4) are interrupted by flat surfaces (10,11) ) adjacent to the two diametrically opposed positions where the disc is connected to one or two shafts. A butterfly valve according to claim 6 characterised in that the flat surfaces (10,11) interrupt the channel (5) between the two edges (3,4) and at least one groove (12,13,14) is provided in the flat surface (10,11) to connect the interactive parts of the channel (5). A butterfly valve according to any one of the preceding claims characterised in that the valve seat (2) comprises an annular elastomeric sealing ring formed with the two generally cylindrical seating surfaces (22,23), each engaging with a respective edge (3,4) of the disc (1) in the closed position.

Inventors: HOLLINGWORTH KEITH JEFFERY, HOLLINGWORTH, KEITH JEFFERY
Applicants: BTR PLC
Application year: 1994
Main classification: F16K1
IPC codes: F16K1